1. Field of the Invention
The present invention relates to a camera system including a camera main body and an interchangeable photographic lens assembly and, more particularly, to focusing therefor.
2. Description of the Prior Art
Since the photographic lens assemblies are interchangeable in a single reflex camera system, various limits are imposed for automatic focusing.
The seemingly easiest means for automatic focusing in a single reflex camera system with which the lenses may be interchanged is to include all the functions necessary for automatic focusing in the photographic lens assembly, that is, to include all the elements, in the photographic lens assembly, which may be required for detection of the focusing state of the photographic optical system and automatic focusing of the optical system based on the detection result. However, with this method, the lens assembly becomes complex in construction, bulky in size and expensive to manufacture.
It has also been proposed, considering the importance of universality for all the interchange lens assemblies, to include a unit in the camera main body which detects the focusing state of the photographic optical system and displays the detected result. With this method, it is indeed possible to perform focusing utilizing the focus display for all the interchangeable lens assemblies. However, it is impossible to accomplish automatic focusing, resulting in inconvenience.